we all know \TeX produces the TeX logo and \LaTeX produces the LaTeX logo. But there seems no command like \BibTeX for producing the BibTeX logo, while Wikipedia adopts a complicated workaround: \mathrm{B{\scriptstyle{IB}} \! T\!_{\displaystyle E} \! X}. So is there no simple command? (I think Bib\TeX is no good because the case does not conform to the official one)

I don't think there's an official BibTeX logo. Usually I adopt \textsc{Bib}\TeX, but also \textsc{Bib}\negthinspace\TeX might be used. The $\mathrm{B\scriptstyle IB}\!$\TeX trick might be used if the font doesn't have small caps.